National Compilation on dynamic ground water resources of India, 2017

Ground Water Resources Assessment is carried out at periodical intervals jointly by State
Ground Water Departments and Central Ground Water Board under the guidance of the
respective State Level Committee on Ground Water Assessment at State Levels and under the
overall supervision of the Central Level Expert Group. Previous such joint exercises were carried
out in 1980, 1995, 2004, 2009, 2011 and 2013.
The assessment involves estimation of dynamic ground water resources or Annual Extractable
Ground Water Resource, Total Current Annual Ground Water Extraction (utilization) and the
percentage of utilization with respect to recharge (stage of Ground Water Extraction). The
assessment units (blocks/watersheds/mandals/talukas/firkas) are categorized based on Stage
of Ground Water Extraction, which are then validated with long-term water level trends. The
previous assessment was carried out using GEC 97 Methodology, whereas the present
assessment is done based on norms and guidelines of the latest GEC 2015 Methodology.
The main source of replenishable ground water resources is recharge through rainfall, which
contributes to nearly 67% of the total annual ground water recharge. India receives about 119cm
of rain in a year but it has great spatial variations. Most part of India receives rainfall mainly
during SW Monsoon season. However, main rainfall season in Tamil Nadu is October–
December. Jammu and Kashmir, Himachal Pradesh and Uttarakhand receive significant rainfall
in all four seasons. Major part of country including Northern, Central and Eastern India receives annual normal
rainfall between 75 and 150cm. Highest rainfall of more than 250cm are recorded in the North
Eastern States and along West Coast in the Konkan region whereas western part ofRajasthan
receives about 30cm of rainfall in an year. The areas on the Western Ghats and the SubHimalayan areas in North East and Meghalaya Hills receive heavy rainfall of over 250cm
annually, whereas the Areas of Northern parts of Kashmir and Western Rajasthan receive
rainfall less than 40cm. The two significant features of India's rainfall are that, in the north India,
rainfall decreases westwards and in the Peninsular India, it decreases eastwards and then
increases in the coastal region.